The climatic evolution of the Atacama Desert during the Cenozoic was mainly driven by long-term tectonic processes, such as the surface uplift of the Andes, but also by changes in the oceanic circulation of the adjacent Pacific Ocean. The timing, forcings, and feedbacks of land-ocean coupling and their impact on the past hydroclimate of the Atacama remain poorly understood. With the proposed project, we want to build on the achievements of the 1^st and 2^nd phases of CRC 1211 and advance the systematic integration of well-dated marine and continental palaeoclimatic records to identify potential links between water availability in the desert and surface water conditions off the coast. Palaeoclimatic archives will include existing and new core and outcrop locations along a transect across the Atacama. We will focus on major transitions in the global ocean-climate system (middle/late Miocene, Pliocene/Pleistocene, Mid-Pleistocene, LGM/Holocene) in order to minimize a potential signal bias from long-term tectonic processes. Properties of the Humboldt Current System (HCS), in particular sea surface temperatures and source waters of coastal upwelling, will be reconstructed on orbital and sub-orbital time scales from geochemical proxy records of foraminiferal tests. Sedimentological as well as organic and inorganic geochemical analyses from available claypan and new lake records in combination with hydrogen isotope values from volcanic glass will provide proxy data on precipitation composition and intensity, and ultimately, moisture sources. Marine and continental records will be synchronized through comprehensive chronostratigraphy (tephro-, magneto-, biostratigraphy, supplemented by radiometric dating). The integrated marine and terrestrial data will be fed into a state-of-the-art, internally fully-coupled paleoclimate and isotopic modelling study to infer patterns of precipitation response to HCS changes.

Two main research hypotheses will be tested:

1. Changes of the Atacama Desert’s hydroclimate since the Miocene coincide with major transitions of the global climate system.
2. Land-ocean coupling, i.e., moisture transport from the Eastern Pacific Ocean, is the main driver of the Atacama Desert’s hydroclimate since the Miocene.

Land‐ocean coupling between the Humboldt Current System and Atacama palaeoclimate in the Neogene

Research areas: Palaeoclimate, Palaeoceanography, Stratigraphy

Principal investigators: Prof. Patrick Grunert, Dr. Jassin Petersen

Today’s hyperarid conditions in the Atacama Desert are determined by the inhibition of moisture influx from the South Atlantic and South‐eastern Pacific and its location north of the Southern Westerlies. However, episodic lacustrine and fluviatile deposits in the Atacama’s hyperarid core document alternations between hyperarid and more humid (semiarid to arid) conditions since the Miocene. The forcings and feedbacks behind these palaeoclimatic fluctuations and in particular their considerable spatial and temporal variability are poorly understood. We intend to explore land‐ocean coupling between the palaeoclimate of the Atacama Desert and the Humboldt Current System (HCS) on different time‐scales throughout the Neogene.

Lower Miocene to Pliocene marine sediments exposed along the coastline of northern Chile (23–30°S) provide an outstanding archive to address these questions. Based on sclerochronology (long‐lived bivalves) and microfossils (foraminifera; assemblages and shell geochemistry) we aim to determine variations in sea‐surface temperatures, upwelling properties and continental runoff on seasonal to orbital time scales. The new low‐ and high-resolution records will provide unprecedented insights into forcings and feedbacks between HCS intensity, ENSO behaviour, upwelling properties, moisture flux to the adjacent continent and palaeoclimatic fluctuations in the Atacama Desert.

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